Lamp reflectors and UV curable compositions useful as basecoats for same

Abstract: Described are preferred UV curable coating compositions which are suitable for use as basecoats in the production of lamp reflectors. Also described are reflector devices and Methods for making them.

Description: BACKGROUND OF THE INVENTION The present invention relates generally to ultraviolet (UV) curable coating compositions and their use as basecoats on metallized molded plastic articles such as lamp reflectors. As further background, metallized plastic molded articles are multi-layer structures which include a molded substrate, a basecoat on the substrate, and a metal film adhered to the basecoat. Further, metallized plastic molded articles may include one or more additional coatings on top of the metal film, for example, they may simply include a topcoat or may include an interlayer and a topcoat. The basecoat is a highly important component of metallized molded plastic articles. The basecoat must adhere well to the plastic substrate and to the metal film. Additionally, the basecoat must be of a uniform thickness across the coated area of the substrate in order to provide a smooth, lusterous appearance to the metallized article and, in the case of metallized articles having exacting optical standards, e.g. reflectors, to preserve the intended optics of the final device. A problem which has been encountered in the prior art is that basecoats have not possessed good edge-coating or leveling properties. Rather, basecoats used in the past have tended to draw or creep away from edges of the substrate thus leaving only a thin coating or no coating near the substrate edges, or have tended to gather at edges and cure to form an undesired ridge or raised portion. In the case of automobile lamp reflectors, this problem has hampered the production of quality, substantially smooth-surfaced reflectors which are used in conjunction with lenses which contain optical structure to achieve appropriate distribution of light. FR 2447794 describes the use of a thermally-cured, powder coating in the manufacture of headlights for the automobile industry. Moreover, a trend exists in the automobile industry to eliminate optical structures from headlamp lenses and rather build them into the associated reflectors. Such reflectors having built-in optical structures include, for example, fluted and/or faceted reflectors (see for instance U.S. Patent Nos. 4,704,661 and 5,034,867). Fluted reflectors include a plurality of convex flutes which introduce alternating grooves and ridges or humps within the reflector surface. Faceted reflectors have a plurality of discreet reflective surfaces which introduce grooves and/or edges between the discreet surfaces. Basecoats having poor edge-coating and leveling properties present special problems with such optical reflectors because thinning or gathering on or between their structural features interferes with the intended optics. Basecoats on metallized plastic molded articles, especially in the case of lamp reflectors, must also exhibit superior thermal stability. Generally, in testing, such basecoats must form stable substrates for the metal film, and the resulting reflectors must exhibit no change in appearance (generally no thermal blistering, cracking or hazing) when subjected to a minimum of 177°C (350°F) for two hours. In the case of lamp reflectors formed from bulk molding compound ("BMC" - glass-reinforced unsaturated polyester resin compositions typically containing up to about 30 wt. % or more glass fibers, e.g. 10%-30%), achieving these aims has been difficult since coatings which are thermally stable have not adhered at all well to the BMC surface. A need therefore exists for Uv curable compositions which are useful as basecoats for metallized molded plastic articles and which exhibit superior flow properties with respect to edge-coating and leveling, and which form cured coatings which adhere well and exhibit thermal stability. WO 92/17337 describes ultraviolet curable compositions containing a blend of first and second acrylated aliphatic urethanes, and their use as topcoats on lenses. The present invention addresses these needs. SUMMARY OF THE INVENTION The present invention provides a metallized plastic molded article comprising: a molded plastic substrate; a UV-cured basecoat comprising an acrylated or methacrylated polyester urethane adhered to said substrate; a metal film adhered to said basecoat so as to form a reflector surface. Accordingly, one preferred embodiment of the invention provides a metallized molded plastics article which is a lamp reflector. The molded plastics substrate comprises a reflector body formed from glass-reinforced unsaturated polyester resin (BMC). The reflector body has an area, usually generally parabolic in shape, on which to form a reflective coating, and at least one aperture defined in the area for receiving a bulb. In accordance with the invention the reflector also includes a UV-cured basecoat adhered to the area. A second preferred embodiment of the invention provides a lamp reflector wherein the UV-cured basecoat compresses a solvent, and, exclusive of the solvent (i.e. not taking into account the weight of the solvent), about 10% to about 20% of an acrylated or methacrylated polyester urethane having a number average molecular weight of about 500 to about 2000, about 40% to about 60% of trifunctional acrylate, about 5% to about 15% of an epoxy diacrylate, and about 3% to about 15% of a photoinitiator. Typically, the solvent will constitute about 75% to about 45% of the overall composition and, taken together, the acrylated or methacrylated polyester urethane, trifunctional acrylate, epoxy diacrylate and photoinitiator will constitute about 25% to about 55% of the overall composition. Such compositions have good leveling and edge-coating properties, and upon curing by ultraviolet radiation form photoreaction products having superior hardness and thermal stability. A third preferred embodiment of the invention provides a lamp reflector, wherein the UV-cured basecoat comprises a solvent and, exclusive of the solvent, about 25% to about 45% of an acrylated or methacrylated polyester urethane having a number average molecular weight of about 500 to about 2000, about 45% to about 65% of a trifunctional acrylate, and about 3% to about 15% of a photoinitiator. As with the second-mentioned embodiment above, the solvent will usually constitute about 75% to about 45% of the overall composition and, taken together, the aciylated or methacrylated polyester urethane, trifunctional acrylate, and photoinitiator will constitute about 25% to about 55% of the overall composition. Such compositions have exceptional flow properties (e.g edge-coating and leveling properties), and form coatings having superior resistance to thermal cracking. fourth preferred embodiment of the invention provides a lamp reflector, wherein the UV-cured basecoat comprises a solvent and, exclusive of the solvent, about 15% to about 30% of an acrylated or methacrylated polyester urethane having a number average molecular weight of about 500 to about 2000, about 1% to about 15% of an acrylated or meLhacrylated polyetlier urethane having a number average molecular weight of about 1200 to about 2600, about 40% to about 60% of trifunctional acrylate, about 5% to about 15% of an epoxy diacrylate, and about 3% to about 15% of a photoinitiator. As with the second-mentioned embodiment above, the solvent will usually constitute about 75% to about 45% of the overall composition and, taken together, the acrylated or methacrylated polyester urethane, acrylated or methacrylated polyeLher urethane, trifunctional acrylate, epoxy diacrylate and photoinitiator will constitute about 25% to about 55% of the overall composition. Compositions of this embodiment have good edge-coating and leveling properties, form coatings having superior resistance to cracking, and demonstrate superior adhesion to BMC's with high glass content. A fifth preferred embodiment of the invention provides a lamp reflector, wherein the UV-cured basecoat comprises a solvent, and, exclusive of the solvent, about 70% to about 90% of an acrylated or meLhacrylated polyester urethane having a number average molecular weight of about 500 to about 2000, about 3% to about 15% of a photoinitiator, and also about 3% to about 15% of a second acrylated or methacrylated urethane having a molecular weight greater than that of the acrylated or methacrylated polyester urethane, and preferably in the range of about 1500 to about 2500. As with the second-mentioned embodiment above, the solvent will usually constitute about 75% to about 45% of the overall composition and, taken together, the acrylated or methacrylated polyester urethane, second acrylated or methacrylated urethane, and photoinitiator will constitute about 25% to about 55% of the overall composition. Compositions of this embodiment have good flow properties and form coatings demonstrating good thermal stability and adhesion to BMC's with high levels of glass content and crosslinking. Additional preferred embodiments of the invention provide metallized plastic molded articles which comprise a molded plastic substrate, a UV-cured basecoat adhered to the plastic substrate which is the photoreaction product of any one of the above-defined compositions of the invention, and a metal film adhered to the basecoat. It will be understood that the use of numerical designations in connection with the above embodiments (e.g. first preferred embodiment, second preferred embodiment, etc.) does not indicate preference of one embodiment over another, but is only for the sake of convenience. Also, unless otherwise specified, percents set forth in this application are percents by weight. One object of the invention is to provide a metallized molded plastics article comprising an ultraviolet curable coating composition that is suitable for forming basecoats for reflectors for vehicle tail lamps, headlamps or foglamps and street or highway lights. Another object of the invention is to provide a metallized molded plastics article comprising an UV-curable coating compositions having excellent thermal stability and adhesion to plastics such as BMC. Another object of the invention is to provide a metallized molded plastics article comprising an UV-curable coating composition which has excellent flow properties such as edge-coating and levelling properties. Still another object of the present invention is to provide a metallized molded plastics article comprising a coated molded plastic substrate, wherein the coating is a UV-cured coating that is smooth and uniform, including at edges or utilitarian structural features of the substrate. Further objects and advantages of the present invention will be apparent from the following description and appended claims. DESCRIPTION OF PREFERRED EMBODIMENTS For the purposes of promoting an understanding of the principles of the invention, reference will now be made to certain embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations, further modifications and applications of the principles of the invention as described herein being contemplated as would normally occur to one skilled in the art to which the invention relates. As indicated above, preferred embodiments of this invention relate to a lamp reflector wherein UV curable coating compositions which comprise an acrylated or methacrylated polyester urethane and are suited for use to form basecoats on metallized molded plastic articles. In this regard, it is important that basecoats on reflectors do not interfere with the intended optics of the reflectors. Thus, the presence of imperfections or bumps in the basecoated reflector can result in parts unsuitable for use, wasting valuable materials and production capacity. The compositions of the present invention provide improved smooth, uniform, adherent and thermally stable coatings, and are thus advantageous for forming basecoats for reflectors such as automobile lamp reflectors. Compositions of the second-mentioned embodiment above requisitely include an epoxy diacrylate (and optionally a tetrafuncational acrylate) in combination with the acrylated or methacrylated polyester urethane, which combination gives high crosslink density and provides uniform coatings of exceptional hardness and superior resistance to thermal cracking. Compositions of the third-mentioned embodiment do not require the inclusion of the epoxy diacrylate, and leave increased levels of trifunctional acrylate, to provide coatings having acceptable hardness and superior resistance to thermal cracking. Compositions of the fourth-mentioned embodiment include a combination of acrylated urethanes in addition to an epoxy diacrylate to provide coatings of acceptable hardness and which have highly superior edge-coating and leveling properties in addition to excellent resistance to thermal cracking. Compositions of the fourth embodiment do not as a requisite include multifunctional acrylates and in addition to having excellent adhesion to highly crosslinked BMC surfaces such as those found on Menzolite, form coatings demonstrating good thermal resistance. As indicated, compositions of the invention will be comprised about 75% to about 45% of inert solvent. This solvent may be a single solvent type or may be a mixture of solvent types. Suitable solvent types include, for example, ester solvents, e.g. ethyl acetate, butyl acetate, and the like, ketone solvents, e.g. acetone, methylisobutylketone, methylethylketone, and the like, alcohols, e.g. butyl alcohol, isopropanol, and the like, and aromatic solvents, e.g. toluene, xylene, and the like. The amount and types of solvents included will vary in accordance with the particular application at hand. For instance, for spray applications, higher levels of solvent will typically be included, while for flow applications, lower levels of inert solvent will be employed. Some preferred compositions of the invention include a substantial proportion of a trifunctional acrylate, that is, a compound having three acrylate functionalities. Representative trifunctional acrylates include pentaerythritol triacrylate (PETA), trimethylolpropane triacrylate (TMPTA), and the like. It has been found that trifunctional acrylates provide optional crosslinking properties without forming coatings which are too brittle, as occurs when large amounts of tetra- or greater functional acrylates are included, or which are thermally instable and lack sufficient crosslink density, as occurs when large amounts of difunctional acrylate are used instead of trifunctional acrylate. As such, for all compositions of the invention including trifunctional acrylate, it is preferred that the amount of trifunctional acrylate present equal or exceed the amount of all other multifunctional acrylates combined (on a weight basis). Other representative multifunctional acrylates which may be included in compositions of the invention include tetraethyleneglycol diacrylate, pentaerythritol tetra acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol diacrylate, pentaerythritol tetra acrylate, and the like. Compositions of the invention may also include a molecule having both acrylate and epoxy functionality. For example, epoxy diacrylates can be used (e.g. as required in the second- and fourth-mentioned embodiments above). Representative epoxy diacrylates include Bisphenol A epoxy diacrylate oligomers available from Radcure Specialities under the names Ebecryl 3700 or Ebecryl 3700-20T (the latter being an 80/20 mixture of the oligomer with TMPTA), Ebecryl 3702, or Ebecryl 3703. When included, the epoxy diacrylate provides increased crosslink density and surface hardness to coatings of the invention. Compositions of the invention include an acrylated or methacrylated polyester urethane, and some also include an acrylated or methacrylated polyether urethane (e.g. as required in the fourth-mentioned embodiment above). In general, in accordance with the present invention, the acrylated polyester or polyether urethanes are preferred. In this regard, as is well known, acrylated and methacrylated urethanes are based on polyether polyols or polyester polyols. Generally, acrylated or methacrylated urethanes are prepared by reacting a diisocyanate, a polyether or polyester polyol, and a hydroxy-terminated acrylate or methacrylate. For example, the polyol can first be reacted with the diisocyanate to form an isocyanate-terminated urethane. The isocyanate-terminated urethane can then be reacted with the hydroxy-terminated acrylate or methacrylate to form the acrylated or methacrylated urethane. In general, the diisocyanate used in the preparation of the acrylated or methacrylated urethane will comprise at least one carbocycle. Representative diisocyanates thus include dicyclohexyl methane-4,4'-diisocyanate (HMDI), isophorone diisocyanate (IPDI), toluene-diisocyanate (TDI), diphenylmethane 4,4'-diisocyanate (MDI), and the like. Diisocyanates including one or more aliphatic carbocycles or alkyl carbocycles (i.e. alicyclic groups), such as HMDI and IPDI, are preferred. The hydroxy-terminated acrylate or methacrylate used to prepare the acrylated or methacrylated urethane may be, for example, hydroxyethyl acrylate, hydroxypropyl acrylate, pentaerythritol triacrylate, diphenyl erythritol tetraacrylate, and trimethylolpropane triacrylate. Preferably, the hydroxy-terminated acrylate or methacrylate has multiple acrylate functionalities, e.g. 2, 3 or 4 acrylate functionalities, with acrylates having 3 or more acrylate functionalities being more preferred. Hydroxy-terminated acrylates or methacrylates containing at least 3 polymerizable unsaturated groups per molecule and further having molecular weights of about 190 to about 500, such as pentaerythritol triacrylate or trimethacrylate, diphenyl erythritol tetraacrylate or tetramethacrylate, and trimethylolpropane triacrylate or trimethacrylate, are more preferred. Preferred resulting acrylated or methacrylated polyester urethanes are at least hexafunctional (i.e. they have at least 6 acrylate groups), and are preferably aliphatic. The polyester polyol component of the acrylated or methacrylated polyester urethane, in accordance with the present invention, will preferably have a molecular weight such that the overall acrylated or methacrylated urethane has a number average molecular weight of about 500 to about 2000, and more preferably about 800 to about 1000. When an acrylated or methacrylated polyether urethane is used in the invention, the polyether polyol will preferably have a molecular weight such that the number average molecular weight of the acrylated or methacrylated urethane is about 1200 to about 2600, more preferably about 1500 to about 2000. More preferred polyether-based acrylated or methacrylated urethanes are formed by the reaction of a hydroxy-terminated acrylate or methacrylate with a molecular weight of about 110 to about 500 with a polyether-based aliphatic urethane (isocyanate-terminated, of course) and having a molecular weight of about 800 to about 2200. The acrylated or methacrylated polyether urethane can be difunctional or have greater functionality, and is preferably aliphatic. Additional information on acrylated and methacrylated urethanes is found in Henry C. Miller, Radiation Curing , pp. 4-9 (May 1984); and JoAnn A. McConnell and F. Kurt Willard, Radiation Curing of Polymeric Materials, pp. 272-283 (1990). As those practiced in these areas will appreciate, many photopolymerization initiators providing good through-cure will be suitable for the invention. These include, for instance, photoinitiators known as Irgacure 651 (2,2-dimethoxy-2-phenol-acetophenone), Darocure 1173 (2-hydroxy-2-methyl-1-phenyl-propan-1-one) and Darocure 4265 (a 50/50 blend of 2-hydroxy-2-methyl-1-phenyl-propan-1-one and 2,4,6-[trimethylbenzoyldiphenylphosphine] oxide), available from Ciba Geigy. The photopolymerization initiator will be included in an amount sufficient to obtain the desired cure response. In preferred compositions of the invention, the photopolymerization initiator is included in amounts of about 3% to about 15% by weight based on solids. As indicated, however, the amount of initiator included will vary based upon many factors such as the cure rate and level of crosslink density for metallization desired. For additional information as to photopolymerization initiators, reference can be made to C. G. Roffey, Photopolymerization of Surface Coatings , Chapter 3: "Photoinitiators and photosensitizers", John Wiley & Sons Ltd (1982). The coating compositions of Lhe invention may also include other conventional additives. For instance, they may contain polymeric or silicone coating surface improvers, flow improvers, dyes, pigments, flatting agents (e.g. wax-coated or non-wax-coated silica or other inorganic materials), anti-foaming agents, light stabilizers, antioxidants, etc. These materials will be included in varying amounts in accordance with the particular use or application desired. When the coating compositions are used as basecoats in the preparation of metallized molded plastic articles, many such additives are of course not necessary. In any event, when compositions of the invention are so used as basecoats, it is important that conventional additives, if included, do not detrimentally interfere with the metallization process. As to its use, the coating composition can be applied by any conventional coating method as known in the art. When used as a basecoat in the preparation of a metallized article reflector surface, the composition is preferably either spray- or flow-applied, to provide a cured film thickness of about 7.62 µm to about 25.40 µm (0.3 to about 1.0 mils), more preferably about 12.70 µm to about 20.32 µm (0.5 to about 0.8 mils). Once applied, the solvents are flashed out, for instance with IR (e.g. for about 1 to 3 min.) or with heated air (e.g. for about 3 to about 15 min.), and the coating composition can be cured by irradiation with ultraviolet rays as is known to those skilled in the art. In this regard, the irradiation is continued until curing is complete, with exposure times typically being less than 300 seconds. Curing temperatures can range from room temperature to the heat distortion temperature of the substrate, while curing distances are typically between about 5.08 cm and 45.72 cm (about 2 and 18 inches) from the UV source. An ultraviolet light source having a wavelength range of between about 1800 Angstroms and 4500 Angstroms is preferred for curing the compositions of the invention. For example, sunlight, mercury lamps, arc lamps, xenon lamps, gallium lamps, and the like may be used, but high pressure or ultrahigh pressure mercury lamps with power outputs of between about 30 W/cm and 400 W/cm provide particularly advantageous rapid cures. A high pressure mercury lamp having an intensity of about 30 W/cm to 400 W/cm is preferred, for a total exposure of between about 2400 and 16000 mJ/cm 2 as measured by a compact radiometer at 60 to 1200 mW/cm 2 , more preferably about 3000 to about 5000 mJ/cm 2 . These curing processes provide good through cure and ensure advantageous coatings which demonstrate good thermal crack resistance. After the coating composition of the invention is cured, in order to form a metallized article, a film of metal, preferably aluminum, is adhered to the cured basecoat composition. This may be conveniently accomplished by coating the basecoat with a deposit of metal by means of vacuum deposition (i.e. by vacuum metallization, sputtering or other suitable methods). Thereafter, one or more additional layers, including a topcoat, can be conventionally applied over the metal film. When used, topcoats are usually about 7.62 µm to about 12.70 µm (about 0.3 to about 0.5 mils) in thickness and can be thermally-cured, UV-cured or other conventional topcoat materials. In accordance with the invention it has also been found that pretreating a plastic surface such as DMC with ultraviolet light provides improved adhesion of compositions of the invention to the surface. When used, pretreatments will generally be for an exposure in the range of 1000 to 10000 mJ/cm 2 as measured by compact radiometer, more usually in the range of about 3000 to 6000 mJ/cm 2 . In the automobile industry, headlamp reflectors, usually having a molded BMC body with a reflector surface defining an aperture adapted to receive an incandescent bulb, must have and maintain appropriate optical properties under high heat conditions. The compositions of the invention adhere excellently when cured onto the glass-reinforced unsaturated polyester resins used in such reflector bodies, resist blistering or cracking under high-heat conditions, and are thus well suited for use in the preparation of automobile headlamp reflectors. For example, BMC/basecoat/metal film/topcoat composites of the invention withstand temperatures of 177°C (350°F) for 2 hours without demonstrating loss of reflectivity (i.e. hazing), blistering or loss of adhesion. In fact, preferred multi-layer structures of the invention can withstand temperatures of at least about 204°C (400°F) for at least 2 hours (and even up to 24 hours or more) without demonstrating any of these flaws, thus highlighting the superior characteristics of the compositions and articles of the invention. Reflectors must also have smooth surface characteristics for optimal performance. The UV-cured film must thus be of uniform thickness across the reflector surface so as to avoid the introduction of undesired bumps or undulations which detract from optical properties of the reflector. As noted above, a primary problem of prior art basecoat materials is that they tend to either creep from edges of the reflector and form a cured film that is too thin or non-existent near the edges, or to gather at edges of the reflector so as to form a cured film having an unwanted bump or raised portion near the edge. To the contrary, compositions of the invention have excellent edge-coating and leveling properties; that is, they are drawn to reflector edges and form cured films of uniform thickness, including at the edges. Thus, not only are compositions of the invention well suited for use as basecoats on standard, smooth-surface reflectors, but also they are particularly advantageous for use on modern reflectors into which optics are built. Such optics typically include a plurality of facets or convex flutes in the reflector body. To provide suitable optics to the reflector, the basecoat must coat the reflector surface, including utilitarian structural features of the flutes or facets, to a uniform thickness. Basecoats which tend to thin out or gather on or in between the facets or flutes would interfere with the intended optics. The compositions of the present invention, having superior leveling properties, will provide coatings of substantially uniform thickness even across such faceted or fluted reflectors, and are thus especially preferred for use thereon. For the purposes of promoting a further understanding of the invention and its preferred features and advantages, reference will now be made to the following specific examples. It will be understood that these examples are given by way of illustration and are not restrictive of the invention. EXAMPLE 1 Coating Composition of Second Embodiment A UV curable coating composition of the second preferred embodiment of the invention was prepared by blending the ingredients set forth in Table 1 in a clean stainless steel vessel equipped with a stirrer. The acrylated urethane used was Ebecryl 8301, which is a acrylated polyester aliphatic urethane having a number average molecular weight of about 900. Part by weight Isopropanol 15.9 Butanol 31.8 Acrylated urethane 4.8 TMPTA 17.9 Ebecryl 3700-20T Epoxy Diacrylate 3.7 Irgacure 651 Initiator 3.8 Anti-foaming agent 0.1 PETA 6.0 MIBK 8.0 Butyl Acetate 8.0 EXAMPLE 2 Production of Headlamp Reflector The coating composition of Example 1 was applied to a glass-reinforced unsaturated polyester (BMC) automobile headlamp reflector body by spray application to allow 12.70 µm (0.5 mil) (12.5 microns) of cured coating thickness. Thereafter, the material was flashed to remove solvents and irradiated with a high pressure mercury lamp of 120 W/cm 2 , with the substrate positioned eight inches from the light source for an exposure of about 3400 mJ/cm 2 in air. The thus obtained coated polyester reflector body was then subjected to vacuum metallization using aluminium to achieve a reflective surface, and a 12.70 µm thick (0.5 milthick) UV-cured topcoat (UVBT 115, Red Spot Paint and Varnish Co, Evansville, Indiana) applied on top of the aluminized surface. The product was subjected to heat treatment in an oven in air at 204°C (400°F) for 2 hours. After this period, no blistering, hazing or loss of adherence was noted. Likewise, subjecting the product to heat treatment in an oven in air at 232°C (450°F) for 24 hours resulted in no blistering, hazing or adherence problems. EXAMPLE 3 Coating Material of Second Embodiment Another UV curable coating composition of the second preferred embodiment of the invention was prepared by blending the ingredients set forth in Table 2 in a clean stainless steel vessel equipped with a stirrer. The acrylated urethane used was again Ebecryl 8301. Part by weight Acrylated urethane 4.8 TMPTA 17.9 Ebecryl 3700-20T Epoxy Diacrylate 3.7 Irgacure 651 Initiator 3.8 Anti-foaming agent 0.1 PETA 6.0 Butyl Acetate 63.7 EXAMPLE 4 Production of Headlamp Reflector The coating composition of Example 3 was applied to a glass-reinforced unsaturated polyester (BMC) automobile headlamp reflector body by flow application to allow 12.70 µm (0.5 mils) of cured coating thickness. Thereafter, the material was flashed of solvents and irradiated with a high pressure mercury lamp of 120 W/cm 2 , with the substrate positioned eight inches from the light source for an exposure of about 3400 mJ/cm 2 in air. The thus obtained coated polyester reflector body was then subjected to vacuum metallization using aluminium to achieve a reflective surface and topcoated as in Example 2. The product was subjected to heat treatment in an oven in air at 204°C (400°F) for 2 hours. After this period, no blistering, hazing or loss of adherence was noted. Likewise, subjecting the product to heat treatment in an oven in air at 232°C (450°F) for 24 hours resulted in no blistering, hazing or adherence problems. EXAMPLE 5 Coating Composition of Second Embodiment Another UV curable coating composition of the third preferred embodiment of the invention is prepared by blendi the ingredients set forth in Table 3 in a clean stainless steel vessel equipped with a stirrer. The acrylated urethane used is Ebecryl 1290. Part by weight Acrylated urethane 4.8 TMPTA 17.9 Ebecryl 3700-20T Epoxy Diacrylate 3.7 Irgacure 651 Initiator 3.8 Anti-foaming agent 0.1 PETA 6.0 Butyl Acetate 63.7 EXAMPLE 6 Production of Headlamp Reflector The coating composition of Example 5 is applied to a glass-reinforced unsaturated polyester (BMC) automobile headlamp reflector body by flow application to allow 12.70 µm (0.5 mils) of cured coating thickness. Thereafter, the material is flashed of solvents and irradiated with a high pressure mercury lamp of 120 W/cm 2 , with the substrate positioned eight inches from the light source for an exposure of about 3400 mJ/cm 2 in air. The thus obtained coated polyester lens body is then subjected to vacuum metallization using aluminum to achieve a reflective surface and topcoated as in Example 2. EXAMPLES 7-10 Additional Coating Compositions of Second Embodiment Additional coating compositions of the second preferred embodiment are set forth in Table 4 below employing Ebecryl 8301 as the acrylated urethane. Ex. 7 Ex. 8 Ex. 9 Ex. 10 /-----------Part by weight----------/ Acrylated urethane 7.8 6.6 9.6 9.6 TMPTA 17.9 17.9 17.9 13.1 Ebecryl 3700-20T Epoxy Diacrylate 3.7 1.9 1.9 3.7 Irgacure 651 Initiator 3.8 3.8 3.8 3.8 Anti-foaming agent 0.1 0.1 0.1 0.1 PETA 3.0 6.0 3.0 6.0 Butyl Acetate 63.7 63.7 63.7 63.7 EXAMPLE 11 Coating Composition of Third Embodiment A UV curable coating composition of the third preferred embodiment of the invention was prepared by blending the ingredients set forth in Table 5 in a clean stainless steel vessel equipped with a stirrer. The acrylated urethane used was Ebecryl 8301. Part by weight Isopropanol 15.9 Butanol 31.8 Acrylated urethane 12.0 TMPTA 20.4 Irgacure 651 Initiator 3.8 Anti-foaming agent 0.1 MIBK 8.0 Butyl Acetate 8.0 EXAMPLE 12 Production of Headlamp Reflector The coating composition of Example 11 was applied to a glass-reinforced unsaturated polyester (BMC) automobile headlamp reflector body by flow application to allow 12.70 µm (0.5 mils) of cured coating thickness. Thereafter, the material was irradiated with a high pressure mercury lamp of 120 W/cm 2 , with the substrate positioned eight inches from the light source for an exposure of about 3400 mJ/cm 2 in air. The thus obtained coated polyester reflector body was then subjected to vacuum metallization using aluminium to achieve a reflective surface and topcoated as in Example 2. The product was subjected to heat treatment in an oven in air at 177°C (350°F) for 2 hours. After this period, no blistering, hazing or loss of adherence was noted. Likewise, subjecting the product to heat treatment in an oven in air at 232°C (450°F) for 24 hours resulted in no blistering, hazing or adherence problems. EXAMPLE 13 Coating Composition of Third Embodiment A UV curable coating composition of the third preferred embodiment of the invention was prepared by blending the ingredients set forth in Table 6 in a clean stainless steel vessel equipped with a stirrer. The acrylated urethane used was Ebecryl 8301. Part by weight Acrylated urethane 12.0 TMPTA 20.4 Irgacure 651 Initiator 3.8 Anti-foaming agent 0.1 Butyl Acetate 63.7 EXAMPLE 14 Production of headlamp Reflector The coating composition of Example 11 was applied to a glass-reinforced unsaturated polyester (BMC) automobile headlamp reflector body by flow application to allow 12.70 µm (0.5 mils) of cured coating thickness. Thereafter, the material was irradiated with a high pressure mercury lamp of 120 W/cm 2 , with the substrate positioned eight inches from the light source for an exposure of about 3400 mJ/cm 2 in air. The thus obtained coated polyester reflector body was then vacuum metallized and topcoated as in Example 2. The product was subjected to heat treatment in an oven in air at 204°C (400°F) for 2 hours. After this period, no blistering, hazing or loss of adherence was noted. Likewise, subjecting the product to heat treatment in an oven in air at 232°C (450°F) for 24 hours resulted in no blistering, hazing or adherence problems. EXAMPLES 15-18 Further Coating Compositions of the Third Embodiment Additional coating compositions of the third preferred embodiment are set forth in Table 7 below. The acrylated urethane is Ebecryl 8301. Ex. 15 Ex. 16 Ex. 17 Ex. 18 /-----------Part by weight----------/ Acrylated urethane 12.1 16.7 16.2 14.1 TMPTA 20.4 28.0 16.2 18.4 Irgacure 651 Initiator 3.8 3.8 3.8 3.8 Anti-foaming agent 0.0 0.1 0.1 0.1 Butyl Acetate 63.7 50.0 63.7 63.7 EXAMPLE 19 Coating Composition of Fourth Embodiment A UV curable coating composition of the fourth preferred embodiment of the invention was prepared by blending the ingredients set forth in Table 8 in a clean stainless steel vessel equipped with a stirrer. The acrylated polyester urethane used was Ebecryl 8301. The polyether-based acrylated urethane used was AB2010, a difunctional material available from American Biltrite and having a number average molecular weight of about 1850. Parts by weight Isopropanol 32.1 Acrylated urethane (polyester) 9.6 Acrylated urethane (polyether) 3.4 TMPTA 16.0 Ebecryl 3700-20T Epoxy Diacrylate 3.4 Irgacure 651 Initiator 3.4 Byk 301 Flow Additive 0.1 MIBK 16.0 Butyl Acetate 16.0 EXAMPLE 20 Production of Headlamp Reflector The coating composition of Example 19 was applied to a glass-reinforced unsaturated polyester (BMC) automobile headlamp reflector body by spray application to allow 12.70 µm (0.5 mils) of cured coating thickness. Thereafter, the material was flashed of solvents and irradiated with a high pressure mercury lamp of 120 W/cm 2 , with the substrate positioned eight inches from the light source for an exposure of about 3400 mJ/cm 2 in air. The thus obtained coated polyester reflector body was then vacuum metallized and topcoated as in Example 2. The product was subjected to heat treatment in an oven in air at 204°C (400°F) for 2 hours. After this period, no blistering, hazing or loss of adherence was noted. Likewise, subjecting the product to heat treatment in a over in air at 232°C (450°F) for 24 hours resulted in no blistering, hazing or adherence problems. EXAMPLE 21 Coating Composition of Fourth Embodiment A UV curable coating composition of the fourth preferred embodiment of the invention was prepared by blending the ingredients set forth in Table 9 in a clean stainless steel vessel equipped with a stirrer. The acrylated polyester urethane used was Ebecryl 8301. The polyether-based acrylated urethane used was AB2010 available from American Biltrite, Lawrenceville, New Jersey. Part by weight Acrylated urethane (polyester) 9.6 Acrylated urethane (polyether) 3.4 TMPTA 16.0 Ebecryl 3700-20T Epoxy Diacrylate 3.4 Irgacure 651 Initiator 3.4 Anti-foaming agent 0.1 Butyl Acetate 64.1 EXAMPLE 22 Production of Headlamp Reflector The coating composition of Example 21 was applied to a glass-reinforced unsaturated polyester (BMC) automobile headlamp reflector body by flow application to allow 12.70 µm (0.5 mils) of cured coating thickness. Thereafter, the material was irradiated with a high pressure mercury lamp of 120 W/cm 2 , with the substrate positioned eight inches from the light source for an exposure of about 3400 mJ/cm 2 in air. The thus obtained coated polyester reflector body was then vacuum metallized and topcoated as in Example 2. The product was subjected to heat treatment in an oven in air at 204°C (400°F) for 2 hours. After this period, no blistering, hazing or loss of adherence was noted. Likewise, subjecting the product to heat treatment in a over in air at 232°C (450°F) for 24 hours resulted in no blistering, hazing or adherence problems. EXAMPLES 23-26 Additional Coating Compositions of Fourth Embodiment Additional coating compositions of the fourth preferred embodiment are set forth in Table 10 below. The acrylated polyester urethane used is Ebecryl 8301. The polyether-based acrylated urethane used is AB 2010. Ex. 23 Ex. 24 Ex. 25 Ex. 26 /-----------Part by weight----------/ Acrylated urethane (polyester) 9.6 9.6 9.6 13.0 Acrylated urethane (polyetlier) 3.4 3.4 3.4 3.4 TMPTA 16.0 12.6 12.6 12.6 Ebecryl 3700-20T 3.4 3.4 6.8 6.8 PETA 0.0 3.4 0.0 0.0 Irgacure 651 Initiator 3.4 3.4 3.4 3.4 Anti-foaming agent 0.1 0.1 0.1 0.1 Butyl Acetate 64.1 64.1 64.1 64.1 EXAMPLE 27 Coating Composition of Fifth Embodiment A UV curable coating composition of the fifth preferred embodiment of the invention was prepared by blending the ingredients set forth in Table 11 in a clean stainless steel vessel equipped with a stirrer. The acrylated polyester urethane used was Ebecryl 8301. Parts by weight Acrylated urethane (polyester) 30.5 Acrylated urethane 3.4 Irgacure 651 Initiator 1.4 Irgacure 500 Initiator 0.7 Butyl Acetate 64.1 EXAMPLE 28 Production of Headlamp Reflector The coating composition of Example 27 was applied to a glass-reinforced unsaturated polyester (BMC) automobile headlamp reflector body by spray application to allow 12.70 µm (0.5 mils) of cured coating thickness. Thereafter, the material was flashed of solvents and irradiated with a high pressure mercury lamp of 120 W/cm 2 , with the substrate positioned eight inches from the light source for an exposure of about 3400 mJ/cm 2 in air. The thus obtained coated polyester reflector body was then vacuum metallized and topcoated as in Example 2. The product was subjected to heat treatment in an oven in air at 204°C (400°F) for 2 hours. After this period, no blistering, hazing or loss of adherence was noted.

Claims: A metallized molded plastics article, comprising: a molded plastic substrate; a UV-cured basecoat comprising an acrylated or methacrylated polyester urethane adhered to said substrate; a metal film adhered to said basecoat so as to form a reflector surface. A metallised molded plastics article according to claim 1 which is a lamp reflector, wherein the molded plastics substrate comprises a reflector body formed from glass-reinforced unsaturated polyester and having an area on which to form a reflective coating and at least one aperture defined in said area for receiving a lamp bulb and wherein the UV-cured basecoat adhered to said area. The lamp reflector of claim 2 and also including a topcoat over said metal film. The lamp reflector of claim 3 wherein said reflector surface does not blister, crack or haze when subjected to 177°C (350°F) for 2 hours. The lamp reflector of claim 3 wherein said reflector surface does not blister, crack or haze when subjected to 204°C (400°F) for 2 hours. The lamp reflector of claim 3 wherein said reflector surface does not blister, crack or haze when subjected to 232°C (450°F) for 24 hours. The lamp reflector of claim 2, wherein the UV-cured basecoat comprises about 10% to about 20% of an acrylated or methacrylated polyester urethane having a number average molecular weight of about 500 to about 2000, about 40% to about 60% of trifunctional acrylate, about 5% to about 15% of an epoxy diacrylate, and about 3% to about 15% of a photoinitiator. The lamp reflector of claim 2, wherein the UV-cured basecoat comprises about 25% to about 45% of an acrylated or methacrylated polyester urethane having a number average molecular weight of about 500 to about 2000, about 45% to about 65% of a triacrylate, and about 3% to about 10% of a photoinitiator. The lamp reflector of claim 2, wherein said UV-cured basecoat comprises about 15% to about 30% of an acrylated or methacrylated polyester urethane having a number average molecular weight of about 500 to about 2000, about 1% to about 10% of an acrylated or methacrylated polyether urethane having a number average molecular weight of about 1200 to about 2600, about 40% to about 60% of trifunctional acrylate, about 5% to about 15% of an epoxy diacrylate, and about 3% to about 15% of a photoinitiator. The lamp reflector of claim 2, wherein said UV-cured basecoat comprises about 70% to about 90% of an acrylated or methacrylated polyester urethane having a number average molecular weight of about 500 to about 2000, about 3% to about 15% of a photoinitiator, and about 3% to about 15% of a second acrylated or methacrylated urethane having a molecular weight greater than that of said acrylated or methacrylated polyester urethane. The lamp reflector of claim 2, wherein said reflector surface comprises a plurality of flutes or facets. The lamp reflector of claim 9, wherein said reflector surface comprises a plurality of flutes.

Inventors: LAKE RANDALL T, LAKE, RANDALL T.
Applicants: RED SPOT PAINT & VARNISH, RED SPOT PAINT & VARNISH CO., INC.
Application year: 1994
Main classification: F21V7
IPC codes: C08G18, F21V7